Every major pond management company I know of in the South advises fertilization, as do most state agencies, on a regular basis to maintain a visibility of 18" or less, which generally entails roughly once a month. I'm not clear on what the disaster might be either. And, as I already noted, it's unlikely that David's pond is more fertile than an old phosphate pit, so any notion that it's at an exceptional level of fertility that I have no familiarity with, seems not sound.

Here's a link to a page on a pond management company in OH's website on which they recommend fertilizing and quote Texas A&M as obviously recommending it as the single most important element of pond management, based on the quote:

http://www.atac.cc/pages/fertilizing_your_pond.asp

The quote from TAMU is, "If you do nothing else, fertilize." That's coming from one of the top, if not the top, universities in Texas when it comes to fisheries science.

Here's a full publication from TAMU, written by a fisheries specialist who works with the university's extension program, recommending fertilization as the cornerstone of pond management in TX, and which specifically states fertilization should be done monthly, or "more frequently if needed, to maintain the bloom":

http://urbanrancher.tamu.edu/retiredsite/aquatic/0904a.pdf

Here are publications from several other Southern states (both universities and DNRs) recommending a monthly program of fertilization as the cornerstone of pond management:

http://www.wildlifemanagement.info/files/fish_ponds_31.pdf

http://www.dcnr.state.al.us/fishing/freshwater/where/ponds/m/f/fertilizing.cfm

http://warnell.forestry.uga.edu/service/library/index.php3?docID=44

http://msucares.com/pubs/infosheets/is0229.htm

http://www.uaex.edu/aquaculture/FSA/FSA9005.htm

http://edis.ifas.ufl.edu/FA003

http://www.seagrantfish.lsu.edu/resources/factsheets/pond_mgmt.htm

I'm more than happy to admit when I'm wrong; but I don't think a strong case could be made that in this case I made a bad recommendation to David, or even one that is anything less than very sound and helpful.